Long-period fiber gratings spontaneously written by a mechanism markedly different from Hill grating formation

Abstract

Pumping a nonlinear germanosilicate fiber with intense near-infrared femtosecond laser pulses for supercontinuum generation may invoke multiphoton-assisted photosensitivity of glasses to write a long-period fiber grating. In sharp contrast to the spontaneous formation of a Hill grating that resonates with the writing wavelength through first-order diffraction, the long-period fiber grating resonates with the writing wavelength through second-order diffraction. This finding highlights the surprising light-matter interaction in a waveguide.

Scalar generalized nonlinear Schrödinger equation-quantified continuum generation in an all-normal dispersion photonic crystal fiber for broadband coherent optical sources

“…The average power of the incident laser beam was attenuated below 1 W before it was launched into the fiber. Higher incident powers could undesirably produce a self-organized long-period fiber grating inside the fiber [ 29 , 30 ]. The coupling efficiency was ~55%, and had little dependence on the incident power, incident beam polarization, fiber length, and individual cleave.…”